Allow overlay preview from non-Canvas origin
Allow overlay preview from non-Canvas origin

flag=none
test plan prerequisites
- Working New Quizzes LTI setup
test plan
- Create a New Quiz
- In the Quiz Instructions, Insert a Course or User Document
- Go to Document Options and set the document to preview in overlay
- Go to Student View and load the quiz
- Click the document link
* Expect the overlay to pop up and load the document

Change-Id: Ic86f2cdcc4f6f3f95fdcdc9981c03365673a9607
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/304825
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>
Reviewed-by: Rajmund Csehil <0e4920c52f84e5c511cbe4d756174eaf35617fe3@instructure.com>
QA-Review: Rajmund Csehil <0e4920c52f84e5c511cbe4d756174eaf35617fe3@instructure.com>
Product-Review: Jon Scheiding <9af6aa5061dd5eef0e85122953253a66930fcf3e@instructure.com>

instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms